Manado was established by the Dutch in the 17th century, and was once praised for its beauty. Unfortunately, the city was heavily bombed during World War II, and again during the Indonesia battle for independence, and the modern reconstruction has left the city less than picturesque.
While for many divers Manado is little more than a way-station on the way to the smaller islands such as Bunaken and Lembeh, there are some rather nice dive resorts along the coast of Sulawesi near Manado, as well as some nice city hotels where you can relax for a night or two after diving.
While diving is the big draw to North Sulawesi, there are other opportunities for adventure on the mainland as well. See the Asia For Visitors guide to Manado for more information and ideas.